Imidazolium compounds



Patented Jan. 3, 1950 IMIDAZOLIUM COMPOUNDS Horace A. Shonle, Indianapolis, and Edwin R. Shepard, Beech Grove, Ind., assignors to Eli Lilly and Company, Indianapolis, Ind., a corporation of Indiana No Drawing. Application July 14, 1945, Serial No. 605,189

'7 Claims.

This invention relates to a group of new organic compounds and more particularly to new substituted imidazolium compounds.

By this invention we have provided new compositions of matter which may be represented by the following formula:

n wherein R and R1 are aliphatic hydrocarbon radicals, one of the radicals having from 1 to 7 carbon atoms and the other having from 7 to 18 carbon atoms, the total number of carbon atoms being from to 25; R2 is an aliphatichydrocarbon radical having from 1 to 7 carbon atoms; X is an anion; and n is an integer from 1 to 3 inclusive.

The compositions of matter of our invention may be regarded as comprising positively charged imidazolium cations which are substituted by aliphatic hydrocarbon radicals and which are combined with negatively charged anions. The aliphatic hydrocarbon groups may be selected from straight chain saturated, branched chain saturated, and straight and branched chain unsaturated groups, such as, for example, the ethyl, isoamyl and allyl groups. The negatively charged anion associated with the imidazolium cation may be any one of a number of negative ions such as, for example, the chloride, bromide, sulfate, acetate, or phosphate ions. By way of example, and referring to the above structural formula, when R is a methyl group, R1 is a decyl group, R2 a methyl group, X a chloride ion and n is l, the compound is 1,3-dimethyl-2-decylimidazolium chloride. Additionally, when R is a dodecyl group, R1 an isoamyl group, R2 an allyl group, X a sulfate ion, and n is 2, the compound is di- (1-dodecyl 2 isoamyl-B-allylimidazolimn) sulfate.

In compounds of this invention the number of carbon atoms contained in the two groups R and R1 ranges from a total of 10 to 25 carbon atoms, The following examples illustrate this limitation: When R is a hydrocarbon group containing 1 carbon atom such as a methyl group, R1 must be a hydrocarbon group containing at least 9 carbon atoms such as, for example, a nonyl group, but it may contain any number up to a total of 18 carbon atoms. Further by way of example, when R1 is a hydrocarbon radical containing 2 carbon atoms such as the ethyl group, R must be a hydrocarbon group which contains octyl group, but it may contain any number up to a total of 18 carbon atoms.

It should be noted that two isomeric forms of our compounds exist simultaneously because of a dynamic equilibrium. Thus, compounds of our invention may be represented by either of the following formulas:

Formula B wherein R, R1, R2, X and n have the same significanoe as before. In Formula A, the nitrogen at position 1 is a tertiary, and the nitrogen at position 3 is quaternary. In Formula B, the nitrogen at position 1 is quaternary, and the nitrogen in position 3 is tertiary. In the specification and claims, we employ for convenience Formula A where R is attached to the tertiary nitrogen at position 1, and R2 is attached to the quaternary nitrogen at position 3. It will be understood that the two forms illustrated are to be regarded as equivalent, and that both forms are to be considered as within the scope of this invention.

The compounds we have invented have several fields of utility. For example, they are efiective in reducing the surface tension of aqueous solutions. They have bacteriostatic properties. Additionally they are possessed of therapeutic qualties which make them suitable for application in the treatment of various bacterial invasions.

Broadly, we may prepare the compounds embodied in our invention by reacting a suitably substituted imidazole with a member of the class of alkylating agents such as, for example, the nitrates, sulfates or halides of aliphatic hydrocarbons. It is usually most convenient to employ the halides since they are readily available, and for therapeutic compounds we prefer to use a halide containing an anion commonly employed in therapeutic compounds, such as chlorine, bromine, or iodine. The reaction is efiected by mixing the substituted imidazole with the halide of the aliphatic hydrocarbon, allowing any spontaneous reaction to subside and subsequently heating the mixture to complete the reaction.

The product may "be purified by recrystallization at least 8 carbon atoms such as, for example, the

or precipitation from suitable solvents or mixtures thereof. The theoretical amount of the aliphatic hydrocarbon halide may be used but it is preferable to use an excess to assure completion of the reaction. The reaction is conveniently,

atoms and R1 is an aliphatic hydrocarbon group containing not more than 7 carbonatoms, may be reacted with a halide of an aliphatic hydrocarbon such as methyl bromide to yield a mixture of the. correspondingly substituted imidazolium bromides. Likewise, by way of example, a group of imidazoles wherein R is an aliphatic hydrocarbon radical containing not more than 10 carbon-atoms and Rr is a mixture of aliphatic hydrocarbon radicals having 11-15 carbon atoms may be-reacted' witha halideof an aliphatic hydrocarbon such asmethyl chloride to yield a mixture of the-correspondingly substituted imidazoliumchlorides. It shouldlbe noted that the compounds. of our invention comprising both of two isomeric forms as mentioned heretofore may be prepared: by either of two routes. An imidazole substituted by the groups R and R1 may be alkylated' with an Rz-containing alkylating agent. Likewise an imidazole substituted by the groups R1 and'Ramay be alkylated by an R-containing alkylating. agent- The same, compound or mixture of compounds results'when R, R1, and R2 are correspondingly identical in each alkylation reaction.

Thecompounds of our invention are salt-like and generally water-soluble, and consequently are subject to many of the ionic reactions which typify soluble inorganic salts. By anionic interchange re actions, one anion may be substituted for another. For. example, by taking advantage of the lower solubilitiy of a substituted imidazolium sulfate as compared'with the solubility of the corresponding imidazolium chloride, the sulfate may be crystallized preferentially from a solution containing the imidazolium, sulfate and chloride ions. 11'- lustrating another method of effecting this conversion; an aqueous solution of substituted imidazolium halide may be shaken with substantially insoluble silver sulfate, whereby the halide ionis removed asinsoluble silver halide leaving in solution the imidazolium sulfate. Additionally, ionic interchange may be effected through the hydroxyl ion as an intermediate. Uponshaking an aqueous solution of a substituted imidazolium" halide with silver oxide, there is formed the cor-'- responding soluble imidazolium hydroxide and insoluble silver halide. Treatment of the solubleimidazolium hydroxide solution with the appropriate acid forms the desired imidazolium compound.

The following examples illustrate methodsby which we may-prepare the new compositionsof matter of our invention.

vEammple 1 1,3-dimethyl-2-n-undecylimidazolium represented by the following formula HCNCHa may be prepared by refluxing a mixture of 171 g. of ethyl laurate and 135 g. of anhydrous ethylene diamine at 110-112 C. for 12 hours. The alcohol and excess: ethylene diamine were: removed by distillation and 172 g. of crude N-lauroyl ethylene diamine was obtained. A mixture of 162 g. of the crude N-lauroyl ethylene diamine and 187 g. of powderedcalcium oxide was heated with stirring at 225 C. for 36 hours. The reaction mixture was cooled to room temperature and extracted three times'with' about 350 cc. of alcohol. The extract was distilled in vacuo and the reaction product, 2 n-undeoyl-4,5-dihydroimidazole, distilled at 180-189" C../1(l mm. It melted at 81-83 C. To

1 56.5 g; of the Z-n-undecyl-4,5-dihydroimidazole was. added 31.7 g. of dimethyl sulfate, the temperature of the reaction during the addition being maintained at about 85 C. About 150 cc. of water was addedandthe reaction mixture stirred until thesolid material had dissolved. An aqueous solution of g. of- 50 percent sodium hydroxideand about 150 cc. of butyl alcohol was added to the reaction: mixture with agitation,.the mixture filtered and the butyl alcohol layer'separated'. The:

reaction product, 1-methyl-2-n-undecyldihydroimidazole, was obtained by evaporation of the butyl alcohol and distillation; of the residue at 167-172 C./6 mm. A mixture of 30.9 g. of 1- methyl-2-n-undecyl-4,5-dihydroimidazole and 3.1 g. of nickel catalyst was heated. at 226-246 C.

until. nomorev hydrogen was. evolved. The desired reaction product.1-methyl-2-n-undecylimidazole was isolated. by distilling the reaction. mixture at 166-203 C./5 mm.

A cold mixture of 1.8 g. of l-methyl-Z-nundecylimidazole and 1.7 g. of methyl iodide was sealed in atube. When the tube and its contents were warmed to about room temperature, a spontaneous reaction took place after which reaction the tube was heated for one hour at -110" C. The tube was then cooled to' about" room temperature and its contents dissolved in about 50' cc. of hot ethyl acetate. The hot solution was treated with decolorizing'carbon, filtered and the filtrate" cooled to about 0 C;, whereupon crystals of" l',3-dimethyl-2-n-undecylimidazolium iodide separated; These were filtered ofi and redissolved in hot ethyl acetate from which solution, uponcooling to about 0 0., there separated substantially pure 1,3-dimethyl-2-n-undecylimidazolium iodide which melted at about 128-130 C.

- liumchloride represented'by the formula decylimidazole and'2 g. of methallyl chloride wassealed in a glass tube and heated to -120" C. for twohours. The tube was cooled toroomtemper-ature, its contents dissolved in about 50 cc.

of hot-ethyl acetate and the hot solution'treated with! decolorizing carbon-and filtered. Upon cooling the filtrate to about 0 0., there separated crystalsof l-methyl-Zen-undecyl-3-methallylimidazolium chloride which, after; recrystallization:

ll fromethylacetate melted at about.183.-1349- C.

Example 3 may be prepared by reacting l-methyl-n-nonylimidazole with methyl iodide as follows:

l-methyl- 2 -n-nonylimidazole was prepared from anhydrous ethylene diamine and ethyl decanoate' in substantially the same manner as was prepared l-methyl- 2 -n-undecylimidazole described in Example 1.

A cold mixture of 1.5 g. of 1-methyl-2-nnonylimidazole and 1.7 g.-of methyl iodide was sealed in a tube. Upon warming to about room temperature the contents of the tube reacted spontaneously after which reaction the tube was heated to 110 C. for one hour. The tube was then cooled to about room temperature, its contents dissolved in about 50 cc. of a hot mixture of ethyl acetate and absolute ethyl alcohol, and the solution treated with decolorizing carbon and filtered. Upon cooling the filtrate to about 0., there separated a crystalline precipitate of 1,3- dimethyl-2-n-nonylimidazolium iodide which after recrystallization from a mixture of ethyl acetate and absolute ethyl alcohol melted at about 127-128" C.

Example 4 l-methyl-Z-n-nonyl-3-ethylimidazolium iodide represented by the formula HC-N-CHa H C 0H I \C,H may be prepared from 1-methyl-2-n-nonylimidazole and ethyl iodide as follows:

A cold mixture of 1.8 g. of 1-methyl-2-nnonylimidazole and 1.7 g. of ethyl iodide was sealed in a tube. The mixture upon warming to about room temperature reacted spontaneously after which reaction the tube was heated to 100- 110 C. for one hour. The tube was then cooled to about room temperature, its contents dissolved in about 50 cc. of boiling ethyl acetate, and the solution treated with decolorizing carbon and filtered. Upon cooling the filtrate to about 0 C., there separated a crystalline precipitate of 1- methyl- 2 -n-nonyl- 3 -ethylimidazolium iodide which after recrystallization from ethyl acetate melted at about 82 C.

Example 5 1-methyl-2-n-nonyl-3 allylimidazolium bromide represented by the formula HC---NOH;

ature the mixture reacted spontaneously alter,

which reactionthe tube was heated to -110 C. for two hours. The tube was then cooled to aboutroom temperature, its contents dissolved in about 50 cc. of a hot mixture of ethyl acetate and dry ethyl .alcohol, and the solution treated with decolorizing carbon and filtered. Upon cooling to about 0 C. a crystalline precipitate of 1-methyl-2-n-nonyl-3-allylimidazolium bromide separated. The precipitate after recrystallization from a mixture of ethyl acetate and absolute ethyl alcohol melted at about 9'798 0.

Example 6 In addition to the method given in Example 5, 1-methyl-2-n-nonyl-3-allylimidazolium bromide represented by the formula BIC-N-CHa Example 7 l-methyl-2-n-undecyl-3-amylimidazolium dide represented by the formula HCNOH3 Cli ll may be prepared from 1-rnethyl-2-n-undecylimidazole and amyl iodide as follows:

A cold mixture of 1.8 g. of 1-methyl-2-n-undecylimidazole and 2 g. of amyl iodide was sealed in a tube and the tube heated to -120 C. for two hours. The tube was then cooled to about room temperature, its contents dissolved in about 50 cc. of hot ethyl acetate, and the hot solution treated with decolorizing carbon and filtered. No precipitate was obtained upon cooling the filtrate to about 0 C. The filtrate was thereupon treated with an excess of petroleum ether which precipitated an oil, 1-methyl-2-n-undecyl-3-amylimidazolium iodide. The oil was purified by dissolving it in hot ethyl acetate, treating with decolorizing carbon, filtering and adding an excess of petroleum ether to reprecipitate 1-methyl-2-n-undecyl-3-amylimidazolium iodide as an oil which was dried in a Vacuum desiccator over sulfuric acid Example 8 V 1-n-decyl-2-methyl-3-ethylimidazolium bromide represented by the formula -H C-NC1o n CH3 Br may be'prepared from 1-n-decyl2-methylimidazole and ethyl bromide.

1-n-decyl-2-methylimidazole was prepared by heating a mixture of 203 g. of N-acetyl ethylene diamine and 560 g. of finely powdered calcium oxide to 225235 C. for 14 hours. After cooling to 90-100 C. the mixture was extracted with three 500 cc. portions of alcohol. The alcohol was evaporated and the residue upon distillation at 195-198 C. yielded 2-methyl-4,5-clihydroimidazole. A mixture of 50.4 g. of 2-methyl-4,5- dihydroimidazole, 52.8 g. of n-decyl chloride and 100 cc. of benzene was refluxed for seven hours and then cooled to 25 C. A solution of 24' g. of 50 percent sodium hydroxide solution in 150 cc. of water was added, the mixture filtered and the benzene layer separated from the filtrate. The benzene was removed in vacuo and the crude 1-n-decyl-2-methyl-4,5-dihydroimidazole distilled at 155-156 C./6 mm. A mixture of 3.2 g. of nickel catalyst and 6.7 g. of l-n-decyl-Z-methyl- 4,5-dihydroimidazole was heated with agitation to 225-235 C. until hydrogen was nolonger evolved. The reaction mixture was cooled to 125 C. and a further amount of g. of nickel catalyst added. The heating was resumed and. continued until hydrogen evolution ceased. The desired 1-n-decyl-z-methylimidazole thus obtained was purified by distilling at 153-160 C./5.5 mm.

A cold mixture of 1.8 g. of l-n-decyl-Z-methylimidazole and 1.7 g. of ethyl bromide was sealed in a tube and the tube was heated at 100-110 C. for two hours. The tube was then cooled to room temperature, its contents dissolved in about 40 cc. of boiling ethyl acetate, and the solution treated with decolorizing carbon and filtered. Upon cooling the filtrate to about C., l-ndecyl-2-methyl-3-ethylimidazolium bromide separated as an oil. The precipitation of the oil was completed by adding anexcess of petroleum ether to the mixture. The oil was separated, redissolved in hot ethyl acetate, the solution treated with decolorizing carbon, filtered, and an excess of petroleum ether added to the filtrate. The 1-n-decyl-2-methyl-3-ethylimidazoliumbromide, which again separated as an oil, was dried in a vacuum desiccator over sulfuric acid.

Example 9 l-n-decyl 2,3 dimethylimidazolium bromide represented by the formula CHS Br may be prepared from l-n-decyl-2-methylimida- Zole and methyl bromide by the sealed-tube reaction as used in the preceding examples. The l-n decyl 2,3 dimethylimidazolium bromide melted at about 83.5-85.5 C.

Example 10 1-n-decyl-2,3-dimethylimidazolium iodide represented by the formula 8. may be prepared by reacting l-n-decyl-Z-methylimidazole with methyl iodide as follows:

A mixture of 45 g. of l-n-decyl-Z-methylimidazole, 35 g. of methyl iodide and 150 cc. of ethyl acetate was allowed to stand in a pressure bottle until the spontaneous reaction had ceased and was then heated to C. for one hour to ensure completion of the reaction. The contents of the bottle were dissolved in 250 cc. of boiling ethyl acetate, the solution treated with decolorizing carbon and. filtered. Upon cooling the filtrate to about 0 0., there separated a precipitate of l-ndecyl 2,3 dimethylimidazolium iodide which upon recrystallization from 400 cc. of ethyl acetate melted at about 108109 C.

Example 11 1-n-decyl-2-methyl- 3 allylimidazolium bromide represented by the formula may be prepared by reaction of 1-n-decyl-2- methylimidazole with allyl bromide in a sealed tube substantially as described. in the preceding examples. 1-n-decyl-2-methyI-3 allylimidazolium bromide melted at about 70-71" 0.

Example 12 1-n-decy1-2- methyl 3 methallylimidazolium chloride represented by the formula melting at 110111 C. may be prepared by reaction of 1-n-decyle2-methylimidazole with methallyl chloride substantially as described in the preceding examples.

Example 13 1-n-tetradecy1-2,3-dimethylimidazolium iodide represented by the formula CH I melting at about 108-110 C. may be prepared by reacting 1-n-tetradecyl-2 methylimldazole with methyl iodide.

The 1-n-tetradecyl-2-methylimidazole used in the preparation was prepared by methods analogous to those used in Example 8 for the preparation of l-n-decyl-2-methylimidazole.

Example 14 1. l-n-octadecyl 2,3 di'methylimidazolium iodide represented by the formula HCN-C1IHH may beprepared by reacting 1-n-octadecy1-2- methylimidazole with methyl iodide in a sealed tube substantially as described. in the preceding examples;

The. 1-n-octadecyl-2-methylimidazole used. in the reaction is prepared by, amethod similai-to that used in Example 3 for the preparation of 1-n-decyl-2-methylimidazole."

7 Example I v I 1,3-dimethyl-2 n-heptadecylimidazolium iodide represented by the formula.

HO-NCH| may be prepared by reacting l-methyl-Z-n-heptadecylimidazole with methyl iodide in a sealed tube substantially as described in the preceding examples.

The 1-methyl-Z-n-heptadecylimidazole used in the preparation is Obtained from ethyl n-octadecanoate and ethylene diamine by a method similar to that used for the preparation of 1- methyl-Z-n-undecylimidazole described in Example 1.

Example 16 A mixture of substituted imidazolium chlorides represented by the following formula:

HC-NOH;

CH3 wherein R1 represents a mixture of aliphatic hydrocarbon radicals derived from commercial ethyl laurate may be prepared by the method of Example 1 except that in place of pure ethyl laurate as used in Example 1 there is used ethyl laurate obtained from Commercial lauric acid, and in place of methyl iodide there is used methyl chloride.

Example 17 A mixture of substituted imidazolium chlorides represented by the following formula:

I \B'2 n wherein R and R1 are aliphatic hydrocarbon radicals, one of the radicals having from 1 to '7 carbon atoms and the other having from 7 to 18 carbon atoms, the total number of carbon atoms being from 10 to 25; R2 is an aliphatic hydrocarbon radical having from 1 to 7 carbon atoms; x is an anion; and n is an integer from 1 to 3 inclusive.

2. A composition of matter represented by the formula: V a

wherein R and R1 are aliphatic hydrocarbon radicals, one radical having from 1 to 7 carbon atoms and the other having from 7 to 18 carbon atoms, the total number of carbon atoms being from 10 to 25; R2 is a saturated aliphatic hydrocarbon radical having from 1 to 7 carbon atoms; X is an anion; and n is an integer from 1 to 3 inclusive.

3. A composition of matter comprising a mixture of compounds, and represented by the formula wherein R is a mixture of aliphatic hydrocarbon radicals having from 8-18 carbon atoms, said radicals being derived from a commercial lauryl alcohol, and Ha is a halogen ion other than fluorine.

4. A composition of matter comprising a mixture of compounds, and represented by the formula wherein R1 is a mixture of aliphatic hydrocarbon radicals having from 11-15 carbon atoms, said radicals being derived from a commercial lauric acid, and Ha represents a halogen ion other than fluorine.

5. 1,3 dimethyl-2-n-nonylimidazolium iodide represented by the formula:

6. 1-n-decyl-2-methyl-3-ethylimidazolium bromide represented by the formula:

HO CHa 7. 1,3-dimethyl-2-n-undecylimidazolium iodide represented by the formula:

- n 2s I HORACE A. SHONLE. EDWIN R. SHEPARD.

(References on following page) 1 1 REFERENCES CITED Number The following referenees are of re ard in the "file at this patent: E V

UNITED STATES PATENTS Number Name Date gg gg 2,042,023 sch'iinhiifer May 26, 1936 12 Name Date Kyfldes July 16, 1946 Kyrides m..- July 16, 1 4 FOREIGN PAfIENTS Country Date Great Britain Feb. 28, 1939 Certificate of Correction Patent No. 2,493,318 January 3, 1950 HORACE A. SHONLE ET AL.

It is hereby certified that errors appear in the printed specification of the above numbered patent requiring correction as follows:

Column 2, lines 9 and 10, for that portion of Formula. A reading column 3, line 22, after the word having insert from column 6, line 22, for O,H," read 0 H line 75, for C H read 0 H column 8, line 35, for C H,," read O H line 64, before 1nstrike out the numeral and period 1.; column 9, line 55, for Lorol read Lorol;

and that the said Letters Patent should be read with these corrections therein that the same may conform to the record of the case in the Patent Ofiice.

Signed and sealed this 25th day of April, A. D. 1950.

[snAL] THOMAS F. MURPHY,

Assistant Oommiaaianer of Patents. 

1. A COMPOSITION OF MATTER REPRESENTED BY THE FORMULA: 